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首页> 外文期刊>Plant and Soil >Soil organic carbon content at a range of north Australian tropical savannas with contrasting site histories
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Soil organic carbon content at a range of north Australian tropical savannas with contrasting site histories

机译：在北澳大利亚热带稀树草原范围内，土壤有机碳含量与地点历史形成鲜明对比

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摘要

Soils play an important role in the global carbon cycle, and can be major source or sink of CO2 depending upon land use, vegetation type and soil management practices. Natural and human impact on soil carbon concentration and storage is poorly understood in native north Australian savanna, yet this represents the largest carbon store in the ecosystem. To gain understanding of possible management impacts on this carbon pool, soil organic carbon (SOC) of the top 1m of red earth sands and sandy loams common in the region was sampled at 5 sites with different vegetation cover and site history (fire regime and tree removal). SOC was high when compared to other published values for savannas and was more comparable with dry-deciduous tropical forests. Sites sampled in this study represent high rainfall savannas of northern Australia (> 1700 mm annual rainfall) that feature frequent burning (2 in 3 years or more frequent) and a cycle of annual re-growth of tall C4 grasses that dominate the savanna understorey. These factors may be responsible for the higher than expected SOC levels of the surface soils, despite high respiration rates. Medium term fire exclusion (15–20 years) at one of the sampled sites (Wildlife Park) dramatically reduced the grassy biomass of the understorey. This site had lower SOC levels when compared to the grass dominated and frequently burnt sites, which may be due to a reduction in detrital input to surface (0–30 cm) soil carbon pools. Exclusion of trees also had a significant impact on both the total amount and distribution of soil organic carbon, with tree removal reducing observed SOC at depth (100 cm). Soil carbon content was higher in the wet season than that in the dry season, but this difference was not statistically significant. Our results indicated that annual cycle of grass growth and wildfire resulted in small carbon accumulation in the upper region of the soil, and removal of woody plants resulted in significant carbon losses to recalcitrant, deep soil horizons greater than 80 cm depth.
机译：土壤在全球碳循环中起着重要作用，并可能成为二氧化碳的主要来源或汇聚地，具体取决于土地利用，植被类型和土壤管理实践。自然和人为因素对土壤碳浓度和储存的影响在北澳大利亚大草原上鲜为人知，但这代表了生态系统中最大的碳储存。为了了解可能的管理对这个碳库的影响，在该地区常见的红土沙和砂壤土的前1m的土壤有机碳（SOC）在5个具有不同植被覆盖和地点历史（火情和树木历史）的地点进行了采样。移除）。与其他已发布的热带稀树草原相比，SOC较高，与干燥的落叶热带森林相比更具可比性。本研究中采样的地点代表了澳大利亚北部的高降雨稀树草原（年降雨量> 1700毫米），其特征是频繁燃烧（3年内发生2次或更频繁），并且以高C4 草为主导的年复生周期稀树草原下层。尽管呼吸速率很高，但这些因素可能是造成表层土壤SOC高于预期水平的原因。在其中一个采样点（野生动物公园）进行的中期防火（15-20年）极大地减少了下层草的生物量。与草为主和经常燃烧的地点相比，该地点的SOC含量较低，这可能是由于减少了对地面（0-30厘米）土壤碳库的破坏性输入。树木的排除也对土壤有机碳的总量和分布都产生了重大影响，树木的清除减少了在深度（100 cm）处的SOC观测值。雨季的土壤碳含量高于旱季，但差异无统计学意义。我们的结果表明，草类生长和野火的年度循环导致土壤上部区域中的少量碳积累，而木本植物的清除导致顽固的深层土壤层（大于80厘米深度）导致大量的碳损失。

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